Bosch Technical Reports, Vol. 8, No. 112, pages 12-14 (1986) disclose a compact disk read-only memory (CD-ROM) on which map data are stored. It is intended that these CD-ROM data will be retrieved using a CD player installed in a motor vehicle and transmitted to the vehicle's positioning and navigation system.
So-called "CD-changers" are known, which have a magazine holding multiple compact disks, any of which the player can select and play. For example, the magazine can simultaneously hold a music or other audio disk and a navigation data disk; when retrieval from a data disk is required, the playing of the audio disk can be momentarily interrupted.